Method of printing sheets

ABSTRACT

A method of printing in which sheets are aerodynamically supported and directed along a path having no abrupt changes in direction to and through individually driven and mechanically synchronized multi-color perfecting towers while the sheet is continuously gripped and moved by a single set of grippers so that only printing cylinders touch the sheet, eliminating sheet transfer between the time the sheet leaves the feeder and the time it reaches the delivery. The sheet and printing cylinders are maintained in a constantly registered condition as the sheet is moved from the feeder to the delivery.

United States Patent 1 Dahlgren 1 Nov. 12, 1974 1 1 METHOD OF PRINTING SHEETS [76] lnventor: Harold P. Dahlgren, 726 Regal Row, Dallas, Tex. 75247 122] Filed: Sept. 10, 1973 [21] Appl.- No.: 395,808

Related U.S. Application Data I [63] Continuation of Ser. No. 250,143, May 4, 1972, abandoned, which is a continuation-in-part of Ser. No. 737,521, June 17, 1968, Pat. No. 3,664,261.

[52] U.S. Cl 101/426, 101/174, 101/216,

101/232 [51] Int. Cl B411 5/08 [58] Field of Search 10l/l83l84,

[5 6] References Cited UNITED STATES PATENTS 522,128 6/1894 Toye 101/183 534,298 2/1895 Toye 101/184 2,366,335 l/l945 Hucks 101/137 2,551,060 5/1951 Simmons 101/232 2,753.798 7/1956 Babst 101/232 2,794,390 6/1957 Burke 101/232 2,911,907 11/1959 Davidson lOl/l37 3,422,757 l/l969 Grabman et all lOl/232 Primary Examiner-Robert E. Pulfrey Assistant Examiner--Edward M. Coven Attorney, Agent, or Fir'mHoward E. Moore; Gerald G. Crutsinger [57] ABSTRACT A method of printing in which sheets are aerodynamically supported and directed along a path having no abrupt changes in direction to and through individually driven and mechanically synchronized multi-color perfecting towers while the sheet is continuously gripped and moved by a single set of grippers so that only printing cylinders touch the sheet, eliminating sheet transfer between the time the sheet leaves the feeder and the time it reaches the delivery. The sheet and printing cylinders are maintained in a constantly registered condition as the sheet is moved from the feeder to the delivery.

5 Claims, 34 Drawing Figures PATENIEUHUV 12 1914 SHEET o1- ur 18 an Q mm a PMENEEMW 12 I974 saw 02 of 18 PATENTEBIIIW 12 1914 SHEET 03 0F 18 QNN M PMEMEW 12 1914 3 sum as a? w PMENYEBW 12 ,9?

sum 10 0? w H5147 EXCHANGE)? RESER VO/zQ ill? PATENTEDNUHZHH 3 84107 saw 18BF18 1 METHOD OF PRINTING SHEETS CROSS REFERENCE TO RELATED APPLICATION This is a continuation of application Ser. No. 250,143, filed May 4, 1972 now abandoned which was a continuation-in-part of my co-pending Application Ser. No. 737,521, filed June 17, 1968, entitled STRAIGHT FEED PRESS, now US. Pat. No. 3,664,261.

BACKGROUND OF THE INVENTION No significant advances have been made presenting new concepts in sheet-fed printing systems for decades. Printing systems designed for the sheet-fed printer are basically the same and allow printing on one side of the sheet at a time, requiring sheets to be turned over and rerouted through the press for single or multi-color perfecting. Sheets are progressively and meticulously transferred in serpentine fashion about transfer and impression cylinders and hopefully registered from one cylinder to another and from one printing unit to another until finally they emerge as a printed product. Printing units must be synchronized for color register through numerous drive and idler gears and consequently presses are extremely complex, massive units which are very expensive to manufacture because of numerous transfer and printing cylinders and mechanisms related thereto.

One or two color sheet-fed perfectors have been developed heretofore However, these machines were specifically designed for specific jobs, such as mass production of paperback books, and are totally unsuitable for high speed production of four folor process printing on both sides of the paper.

Heretofore no commerically successful sheet-fed press had the capability of printing on two sides of a sheet in as many as four colors by passing the paper throughthe press one time.

It is the common and accepted practice in the printing industry to run a sheet to be printed through the sheet-fed press a multiplicity of times to attain multicolor printing on two sides of a sheet. After each pass of the sheet through the press, the plates must be changed and the press' made ready for the next pass to apply other colors or to print on the back of the sheet. It is readily apparent to those skilled in the printing art that a considerable amount of time is spent making sheet-fed presses ready to print and in attaining proper registry of the numerous components of the press.

In a typical four-color one-side printing press a sheet delivered from the feeder is caught by the gripper bars of a first transfer cylinder. The sheet is folded around the transfer cylinder and carried to the grippers on the first impression cylinder where the grippers of the transfer cylinder release the paper and it is caught by the grippers of the impression cylinder. The grippers on the impression cylinder rotate the paper into contact with thh blanket cylinder where printing is accomplished in one color on one side of the sheet. When the grippers on the impression cylinder release the sheet, grippers on a second transfer cylinder grasp the sheet, causing the printed surface to be in contact with the transfer cylinder while it is rotated to the grippers of a second impression cylinder. The grippers of the second transfer cylinder release the sheet as it is caught .by the grippers of the second impression cylinder which rotates the sheet into contact with a second blanket where a second color is applied to the same side of the sheet. Grippers on a third transfer roller catch the sheet as it is released by the grippers of the second impression cylinder and the printed surface is again brought into contact with a transfer cylinder while it is being delivered to the grippers of a third impression cylinder. This process is continued until the sheet passes to delivery. When one side of the sheet is completed, the press is replated the sheets are turned and re-fed through the press to print the other side of the sheet.

Virtually all sheet-fed printing presses heretofore developed have the characteristic of feeding the sheet serpentine fashion through the press while the grippers associated with each cylinder catch the sheet as it is being released by the grippers of the previous cylinder.

One of the major problems encountered by the printing industry lies in synchronizing the various cylinders whereby the sheet will be grasped and released at the proper moment for maintaining registry between the cylinders of successive towers so that colors do not overlap or separate.

Chains have been used in the past with limited success to transfer sheets from one printing station to another. However, grippers supported by the chain were positively indexed to the printing station cylinders in an attempt to regain register which was periodically lost between printing stations.

A chain has inherent limitations as a smooth transfer media because chordal motion of the links limit smooth flow; linear deformation of the chain results from numerous pivot joints. Lubrication requirements at joints, to help prevent wear, noise, shock and vibration, present maintenance problems.

The gripper and chain transfer media could not, by itself, register the sheet between printing stations, even with the chain travelling precisely at cylinder speeds. As a compromise, grippers had to be loosely supported on the chain, moved from normal position, and indexed to printing station cylinders prior to actual sheet transfer at the cylinder. As soon as sheet transfer was accomplished and the gripper became separated from index with the cylinder, the gripper jumped or jerked back into its normal relation with the chain.

In the transfer system employed and disclosed herein, there is no contact between tape directed gripper bars and the printing cylinders thereby eliminating shock, vibration, wear, noise, mis-register and other apparent problems accompanied by chain supported grippers being indexed to cylinders. The printing cylinders are entirely independent of the sheet transfer mechanism and vice versa except for speed synchronization of cylinder surface speed with that of the tape.

Another problem has been the offsetting of wet ink on transfer cylinders from the freshly printed surface on the paper and consequently back on to the next sheet that is passed through the press. I-Ieretofore,v

presses with a multiplicity of towers for applying more than one color of ink to the sheet were driven by a common drive through a complex gear train or through long shafts which have inherent distortion thereby increasing the problem of synchronizing components of the press thereby making precision registry more difficult.

Typical four-color one-side printing presses have an I average of about 20 cylinders including the plate cylin- 

1. A method of sheet-fed printing comprising, providing a sheet; providing a printing press having at least two adjacent rotatable printing cylinders; positioning the leading edge of a sheet in a gripper element; moving the gripper element toward and between the printing cylinders in a straight line substantially normal to a line intersecting the tangent point of the cylinders and the longitudinal axes thereof; printing on both sides of the sheet carried by the gripper element at substantially the same instant; and moving the gripper element away from the printing cylinders in a substantially straight line to disengage the sheet from surfaces of each of the printing cylinders whereby the sheet when passing between the cylinders is maintained in substantial line contact with the cylinders.
 2. The method of claim 1 with the addition of the step of shielding the sheet adjacent opposite sides of the path along which the gripper element is moved to prevent movement of air currents transversely of the direction of travel of the sheet.
 3. A method of printing on a sheet as said sheet is moved between adjacent rotating printing and impression cylinders comprisng steps of, providing a sheet having a length which is less than the circumference of the printing cylinder; attaching the sheet in a gripper element adjacent the leading edge of the sheet; moving a conveyor at a uniform speed in non-driving relation to printing and impression cylinders to move the gripper element; guiding the gripper element toward, between and away from the printing cylinder and the impression cylinder such that the sheet substantially bisects the cusp area formed by adjacent converging surfaces of the printing and impression cylinders; and printing on the sheet as it is moved between the printing cylinder and the impression cylinder.
 4. A method of printing comprising the steps of: positioning the leading edge of a sheet in a gripper element; moving the gripper element along a substantially straight path toward, through and away from a plurality of printing stations whereby the sheet when passing between adjacent cylinders in thh printing station is maintained substantially in line contact with the cylinders; urging the gripper element laterally across the path into engagement with an indexing surface adjacent each printing station; and disengaging the leading edge of the sheet from the gripper element after the sheet has been moved through each of the printing stations.
 5. A method of transferring sheets to, through and out of a printing nip between a pair of adjacent cylinders, at least one of which has a longitudinally extending gap formed therein comprising the steps of: rotating an endless flexible tape having spaced gripper elements secured thereto such that each gripper element moves along substantially straight tracks passing adjacent opposite ends of the printing nip; restraining each gripper element Against longitudinal movement transversally of one of the tracks; rotating the cylinders such that each gripper element passing therebetween will be positioned in a longitudinally extending gap; positioning the leading edge of a sheet in a gripper element such that movement of the gripper element will transfer the sheet to, through and out of the printing nip; and disengaging the leading edge of a sheet from the gripper element after the sheet has moved out of the printing nip. 